See the Related Link below. It is a meeting of Christians from many denominations (eg catholic, Methodist, Anglican, Baptist and so on) in order to discuss doctrine, liturgy,
… mission or any aspect of Christian life that is not denomination-specific. . Catholic Answer An Ecumenical Council, literally "universal" is commonly used to identify the general councils of the Church. With the rise of the movement for Christian unity, it has become synonymous with "striving for reunification" among the separated Churches of Christendom. The second sense is the one that is given in the definition above. The first, and classic sense of the word is given in the 21 Ecumenical Councils of the Church beginning with Nicaea I (325), and ending with Vatican Council II (1962-65), see the link below: (extracted from Modern Catholic Dictionary by John A. Hardon, S.J. Doubleday & Co., Inc. Garden City, NY 1980) (MORE) 
